1. Field of the Present Invention
The present invention generally relates to the field of data processing systems and more particularly to energy consumption conservation in partitioned data processing systems.
2. History of Related Art
In the field of data processing systems, the demand for server consolidation solutions is growing. Driven by corporate efforts to reduce hardware costs, server consolidation includes tools that enable systems administrators to run multiple applications and, significantly, operating systems in isolation on a single server. Employing server consolidation concepts, an enterprise could consolidate applications and services that it currently deploys on multiple servers thereby eliminating the need for large numbers of server boxes. Consolidation is facilitated by the related concepts of virtualization and partitioning. Both have existed on mainframe computers for years, but are now becoming increasingly demanded and increasingly viable options for Unix and Intel platforms.
Logical partitioning refers to the ability to make a single multiprocessor system behave as if it were two or more independent systems. Each logical partition (LPAR) represents a division of resources within the system. Each partition is “logical” because the division of resources is not necessarily tied to physical, hardware-defined boundaries within a system although some machines, the IBM xSeries 440 for example, have some type of modular construction where several machines that could be standalone systems are tightly connected into a larger system. The primary resources in a typical system include its processors, main storage (system storage), I/O buses, and I/O adapters (IOA's). Each logical partition is configured to operate as an independent logical system, but each partition may share physical system attributes such as the system serial number, system model, and processor feature code. Other system attributes may vary among partitions. For example, each partition in a conventionally implemented LPAR has dedicated hardware such as processors, main storage, and I/O devices. For information on LPAR implementation details, the reader is referred to Slicing the AS/400 with Logical Partitioning: A How to Guide (SG24-5439-00) and Capacity Planning for Logical Partitioning on the IBM iSeries Server (SG24-6209-00), which are both available as IBM Redbooks (www redbooks ibm com).
Logically partitioned systems are gaining in popularity as a means for implementing a server consolidation strategy. Logically partitioning a system's resources (processors, memory, disk storage and other I/O devices, and so forth) enables logical isolation of software such that, for example, each partition runs its own operating system (OS). Logical partitions also have some hardware fault tolerance if configured properly. Interactive and batch workloads that may not run well together on a single machine can be isolated and run more efficiently in separate partitions. Similarly, production and test environments can be implemented on a single physical system. Thus, a customer can consolidate several systems into one system with logical partitions thereby eliminating the need for and expense of additional hardware.
Historically, LPAR systems were more or less static meaning that the resources assigned to a particular partition did not vary over time unless a complete reconfiguration (typically including a system boot) was performed. LPAR systems typically employ low level software, alternatively referred to as a virtual machine monitor or a hypervisor that is responsible for managing the various partitions including the resources available to each partition. Developments in hypervisor code have led to the emergence of dynamic logical partitioning (DLPAR) systems.
Concurrent with the increasing emphasis on consolidation, enterprises are also becoming increasingly cognizant of operating costs and, more specifically, the energy consumption costs associated with information technology infrastructure. Historically, the goal of reducing server operating costs has received a low priority relative to the goals of performance (low latency and high throughput), reliability, availability, and security. As enterprises continue to pack computational capability into increasingly dense configurations, however, energy consumption and the resulting heat dissipation have become important not just from a cost perspective, but also from performance and reliability perspectives as well.
It would be desirable, therefore, to incorporate power awareness functionality into the hypervisor used on server systems supporting logical partitioning.